Method for combined fine boring and honing machining, and machining plant for executing the method

ABSTRACT

A method for fine boring of internal surfaces of bore holes in work pieces as well as a machining plant for executing this method. The fine machining, fine boring, and honing include fine boring of a bore hole of a work piece using a fine boring tool; transferring the work piece into a honing device; measuring the fine bored bore hole with a measuring device associated with the honing device; and controlling the operation of the fine boring device depending on the bore hole measuring signal received by the measuring device. An output fine boring machining, arranged directly upstream of the transfer, is dimensioned as semi-finishing machining, and is carried out with a fine boring tool having at least one adjustable cutting edge. The position of the adjustable cutting edge is controlled depending on the bore hole measuring signal.

BACKGROUND OF THE INVENTION

The invention refers to a method suitable for fine machining of cylindrical internal surfaces of bore holes in work pieces by fine boring and subsequent honing, as well as to a machining plant for the execution of the method. The preferred field of application is the fine machining of essentially cylindrical plain bearing surfaces in components for motor construction, in particular the machining of cylindrical bearing surfaces of a motor block or the machining of connecting rod eyes in connecting rods.

Conventional honing is a metal-cutting method with geometrically undefined cutting edges, in which multiple edge honing tools perform a cutting movement consisting of two components that leads to a characteristic surface structure of the machined internal surface with crossed over machining marks. Honing makes the production of finished machined surfaces possible that meet extremely high demands with reference to dimensional and shape tolerances, as well as with reference to the surface structure. Accordingly, for example, in motor construction cylindrical bearing surfaces, i. e. internal surfaces of cylinder bore holes in a motor block or in a cylinder liner to be installed in a motor block, bearing surfaces for shafts, and the cylindrical internal surfaces in connecting rod eyes undergo a honing machining. The machining of cylindrical bearing surfaces typically involves several different successive honing operations, for example coarse honing with rather strong material removal for producing the desired macro shape of the bore hole, and finish honing with less material removal in order to produce the surface structure required on the finished work piece.

In order to prepare the work pieces to be machined for honing purposes, upstream of the honing process a coarse machining can be provided by fine boring, that is sometimes also known as precision lathe or precision spindling. For example, sometimes when connecting rods are machined, between the break separation and the honing serving as the finish machining a precision turning operation is carried out. Suitable fine boring operations serve for fixing the desired position and angular position of the bore hole. Thus, in the subsequent honing operation of the bore hole with a honing tool movably mounted by universal joint or limited in some other way, the bore hole axis defined by the fine boring operation can be traced. An essential task of the honing operation with a reduced oversize compared with the fine boring is the production of the required surface coarseness, the cylindrical shape and the diameter.

A method of this type and a machining plant of this type are known from the international patent application WO 2008/009411.

BRIEF SUMMARY OF THE INVENTION

Referring to this state of the art, it is a problem of the present application to design the process chain of fine boring—honing more efficiently.

In order to solve this problem, the invention provides a method with the characteristics of claim 1 as well as a machining plant with the characteristics of claim 30. Advantageous developments are presented in the dependent claims. The wording of all claims becomes the content of the description by reference.

According to a formulation of the invention, a method for fine machining of internal surfaces in work pieces by fine boring and subsequent honing has the following steps:

Fine boring of at least one bore hole of a work piece by means of a fine boring tool of a fine boring device for producing a fine bored bore hole;

Transfer of the work piece in a machining position of a honing device for machining the fine bored bore hole by means of a honing tool of the honing device;

Measuring of the fine bored bore hole by means of a measuring device allocated to the honing device for producing at least one bore hole measuring signal representing the properties of the fine bored bore hole; and

Control of the operation of the fine boring device depending on the bore hole measuring signal,

-   -   wherein an output fine boring machining, provided immediately         upstream of the transfer is dimensioned as semi finish         machining, and the output fine boring machining is executed with         a fine boring tool having at least one adjustable cutting edge,         wherein the position of the adjustable cutting edge is         controlled depending on the bore hole measuring signal, and that         during an intake honing machining arranged downstream of the         transfer an oversize of at least 100 μm is removed.

A machining plant suitable for performing the method for the fine boring of cylindrical internal surfaces of bore holes in work pieces by fine boring and subsequent honing comprises:

A fine boring device with at least one fine boring spindle for carrying a fine boring tool, as well as a fine boring control unit for controlling the operation of the fine boring device;

A honing device with at least one honing spindle set up for carrying a honing tool, as well as a honing control unit for the control of the operation of the honing device;

Wherein the honing device has at least one measuring device for measuring a fine bored bore hole machined by the fine boring device, and for producing a bore hole measuring signal representing the quality of the fine bored bore hole, and the fine bore control unit is configured for controlling the operation of the fine boring device depending on the bore hole measuring signal.

The invention provides that a larger part of the material removal is shifted from the fine boring machining and the fine boring, respectively, towards honing. Therefore it is suggested, according to the invention, that the intake honing machining, arranged downstream of the transfer, removes an oversize of at least 100 μm.

Compared with boring tools working with geometrically defined cutting edges, honing tools have a considerably longer lifetime, so that a larger production rate can be machined without changing the tools. While with boring tools a wear of the geometrically defined cutting edges may lead to a slow change of the engagement relations, and thus to a reduction of the quality of the surface and accuracy of shape, the cutting performance of honing tools remains essentially constant because of the self-sharpening effect of the cutting groups provided with bound cutting bodies during the entire lifetime, so that even with large production rates of machined work pieces and larger material removal per bore hole a rather constant quality of shape and surface micro structure can be achieved.

For example, it is provided, that an output fine boring machining, arranged immediately upstream of the transfer, is dimensioned as semi finishing machining. In the state of the art the metal cutting machining of a geometrically defined cutting edge is divided in a coarse machining or coarse bore hole machining (rough boring machining), a semi finish machining and a finishing machining. The finishing machining had the highest quality of the machined surface on the fine boring side. This level of quality is not required on the side of the fine machining anymore, this finishing machining is deleted.

When a part of the machining task is shifted away from the fine boring towards honing, this can increase the productivity of the entire process.

Additionally, through the fact that the position of the adjustable cutting edge is controlled automatically depending on the bore hole measuring signal, a continuous or immediate compensation of wear during the output fine boring operation becomes possible, so that, first of all, variations of the diameter of the bore holes in the work pieces transferred to the first honing station can be essentially reduced compared with conventional processes. These variations have been reduced conventionally by arranging a finishing machining (fine boring with little material removal) downstream of the semi finishing machining, in order to correct errors of the diameter after the semi finishing machining by another fine boring operation. This fine boring station, usually controlled through the measuring results of a separate verifying station, can thus be deleted. The first honing level (intake honing operation) can be dimensioned for smaller variations of the diameter, what makes perfecting for large material removal easier. On the other hand, the specifications can be relaxed for the last fine machining step with regard to roundness, straightness and parallelism as well as coarseness of the surface.

In the state of the art it has also been known to provide a measuring station associated with the fine machining after the finishing machining, that determined bore hole measuring values representing the fine bored bore hole. The suggestion according to the invention does without this separately upstream of the honing device arranged measuring station, so that also costs are reduced for the operation of the method according to the invention as well as for the machining plant according to the invention.

The term “output fine boring machining” indicates here the last machining step where a metal cutting tool with defined cutting edges, typically a fine boring tool, is employed.

The term “intake honing machining” indicates here the first honing machining step following a last machining with defined cutting edges. In a conventional multi step honing machining, the intake honing machining corresponds usually with the “coarse honing” with regard to the position in the process chain.

In connection with this application, oversizes, material removals, allowances, measuring for roundness, straightness or parallelelism are always referred to the diameter of the bore hole.

As far as in the frame of this application cylinders or cylindrical internal surfaces are mentioned, this is equivalent with any prisms or prismatic internal surfaces, for example with elliptic basic surface. Because of the longer lifetimes of the honing tool in direct comparison with a machining tool with geometrically defined cutting edges, it is possible in a development, that through the intake honing machining an oversize is more than 150 μm. Preferably during the intake honing machining an oversize of maximum 400 μm is removed, preferably the upper limit is 300 μm.

In the method a measuring device arranged after the fine boring operation and belonging to the honing device is used for determining the machining result of the preceding fine boring operation. The bore hole measuring signal can contain in particular information about the diameter and the macro shape of the fine bored bore hole after fine boring, for example with reference to measuring accuracy, roundness, cylindrical shape and/or profiling in axial direction (conical form, barrel form, bell mouth etc.). If necessary, also information about the position of the bore hole with reference to a target position and/or information about the surface quality can be contained.

The measuring of the fine bored bore hole by means of a measuring device associated with the honing device, i. e. the output control of the fine boring operation, can be performed in the machining position of the work piece provided for the subsequent honing machining, so that a transfer from the fine machining device to the honing device can be carried out, if necessary without stop-off, and thus very fast. Thus measuring of the fine bored bore hole by means of the measuring device can be done in a machining position of the work piece within the honing device.

For example, a honing device can be provided containing an integrated measuring device for an in-process diameter measuring for the diameter turning-off of the honing process and for an in-process correction of the bore hole shape. This in-process diameter measuring device can be used for capturing the diameter of the fine bored bore hole prior to the start of the honing machining or in the starting phase of the honing machining in one or more measuring levels, and for producing a corresponding bore hole measuring signal describing the fine bored bore hole. This bore hole measuring signal (or a signal deduced from it) can be returned to the fine boring device for wear compensation.

The suggestion does not only comprise the solution in which the measuring device is integrated in the honing device, but also a solution in which the measuring device in the honing device is arranged as separate measuring station in the direction of material flow prior to the intake honing machining. An arrangement of this kind also leads to an improvement of the entire process.

For the measuring (either with measuring device integrated in the honing tool or with separate measuring station) of the fine bored bore hole in many cases a rather high accuracy of measuring is an advantage for allowing a precise control of the subsequent honing operations. Preferably, the fine bored bore hole is measured with a measuring accuracy of less than 10 μm (with reference to the diameter), the measuring accuracy being in particular in the range between 2 μm and 6 μm.

In a modification of the method the fine bored bore hole is measured by means of at least one measuring sensor attached to a honing tool. The honing tool, i. e. the machining tool, thus serves as sensor carrier for the measuring sensor, so that the associated honing spindle and its control can be used for introducing the measuring sensor in the fine bored bore hole, if necessary for moving the measuring sensor within the fine bored bore hole for the measuring, and also, after finishing the measuring, for leading the measuring sensor out of the bore hole. Thus, considerable effort for constructing a separate measuring station can be saved.

If the measuring sensor is realized in a separate measuring station, at the measuring station a separate sensor carrier for the measuring sensor is provided, that can move in such a way that the measuring sensor can be introduced in a fine bored bore hole.

If necessary, the measuring sensor attached to the honing tool can be used, after the measuring of the not yet honing machined fine bored bore hole, also for monitoring the progress of a subsequent honing operation. The result thus can be a multiple use of the measuring device associated with the honing device, while, at the same time, the effort concerning the equipment for handling the measuring sensor is reduced.

In many honing processes, after starting the honing process, several tenths of seconds or even whole seconds pass by before the honing tool or the machining elements attached to the honing tool (in particular honing sticks, honing stones) come into machining engagement with the work piece surface, and thus change the fine bored bore hole. In addition to that, often the boring is only slightly changed during the first tenths of seconds or whole seconds of the honing engagement. Therefore, the period between the start of the honing process and the start of the substantial material removal can be used for capturing the bore hole measuring signal. Therefore, in a development the bore hole measuring signal for describing the fine bored bore hole is captured while the honing process has already started. It is also possible, that the bore hole measuring signal for describing the fine bored bore hole is captured completely prior to the start of the honing process, that is when the honing process has not yet been started. In some embodiments, the capturing of the bore hole measuring signal starts prior to the start of the honing process, and extends even in the starting phase of the honing process, for example in the time when the machining elements of the honing tool are adjusted with rather high adjustment speed in the direction of the surface to be machined, before the actual machining engagement starts. If at least a part of the measuring time required for capturing the bore hole measuring signal is in the phase after the start of the honing process, the result will be a considerable gain in time and the machining times can be shortened.

In the measuring device associated with the honing device different measuring principles can be used alternatively or in combination. In some embodiments the measuring device is a pneumatic measuring system (called also “aerial measuring system”). Measuring devices with tactile measuring sensors (stylus or the like), capacitive, inductive and/or optical measuring principles are also possible.

In some modifications of the method the work piece is transferred, after finishing the fine boring operation, from the fine boring device directly in the machining position at the honing device. It can be, in particular, that in the direction of material flow between the fine machining device and the honing device no measuring device is provided for the quantitative dimensional measuring of the fine bored bore hole.

If necessary, on the transfer path a “bored control” can be provided that determines by way of a yes/no decision whether a regular fine boring operation has been performed, so that at the beginning of the subsequent honing operation the honing tool can be inserted without colliding with the tool in the bore hole. This control device can be constructed simply and economically as an exact dimensional measuring of the bore hole is not required.

In some embodiments the honing device comprises a verifying device for the measuring of the honed bore hole after finishing the (one or more step) honing operation. The verifying device produces one or more verifying signal/s, from which information about the diameter, the macro shape and/or the surface quality of the honed bore hole can be deduced. This information can be used for qualifying the finished work piece.

The verifying device can be dimensioned as fixed measuring device with higher accuracy of measuring than the highly dynamic measuring devices for the in-process measuring during the honing operation.

In a development the verifying device is connected with the honing control provided for controlling the honing operation such that it transmits signals, and the honing control unit is configured for controlling the operation of the honing device depending on measuring signals of the verifying device. As the verifying device allows a fixed measuring apart from the machining process with high accuracy, the return of the verifying signals can be used for the honing control for further increasing the machining accuracy in order to reduce, for example, the scattering of diameters of the machined work pieces. Thus a greater stability of the machining process can be achieved with a lower reject rate and smaller tolerances. This additional verifying and signal return has proved very advantageously, even if through the measuring sensors provided at the honing tools already an in-situ measuring of the honed bore hole can be performed during the honing operation.

The productivity is further increased by the fact that the position of the adjustable cutting edge is controlled automatically depending on the bore hole measuring signal. In the control a continuous variance comparison of the bore hole measuring signal with a reference value is carried out, and a wear occurring at the geometrically determined cutting edge is reduced immediately by re-adjusting or adjusting of the cutting edge.

Furthermore, it is provided, that the output fine boring machining is dimensioned as position and angle determining semi finish machining. In contrast to that, it is alternatively also possible, that the intake honing machining performs also a “position honing”, i. e. this working step determines position and angle of the bore hole instead of the output fine boring machining.

If the step of the intake honing machining is used for correcting the angular position and/or position of the fine bored bore hole, it may be provided, that the work piece holding device during the intake honing machining provides essentially the same seat as the work piece holding device during the output fine boring machining. In particular for this case a rigid work piece holding device has to be provided through which the position of the work piece can be determined in the machining position in the honing device fixed with reference to the frame. The result is, that the work piece can not escape to the side when diagonal forces occur. The same indexing as in the fine boring may be provided. The work piece is defined in such a way that the target position of the bore hole axis of the bore hole to be machined by honing is coaxially to the rotational axis of the honing spindle. In connection with a rigid coupling of the expandable honing tool to the honing spindle (directly or via a rigid driving rod) thus the opportunity is created to correct the bore hole position and/or angular position by honing, if these parameters are not in the specification after finishing the output fine boring machining.

The expandable honing tool is, as a rule, inserted eccentrically in the bore hole, when the bore hole is not perfectly positioned, and corrects the bore hole position and/or angular position during expansion of the material removal, that is in the beginning uneven and then becomes increasingly more uniform in the course of the intake honing machining. If, however, the bore hole is already positioned correctly, automatically a centered insertion of the honing tool takes place, and the bore hole is not shifted during honing in the course of the expansion (enlargement of the diameter) of the honing tool, but only uniformly expanded on all sides until the intended target dimension after the intake honing machining.

In a development of the invention it is provided, that the intake honing machining is arranged directly downstream of the transfer. In this modification a transfer is performed directly from the output fine boring machining to the intake honing machining. It is not provided here to buffer the work piece to be machined, so that the machining plant according to the invention is constructed short, and the entire machining is executed without interruption. In this modification the measuring device is located in the honing tool.

According to the suggestion, the quality requirement of the bore hole after the output fine boring is lowered compared with conventional processes, so that it is possible to concentrate in the output fine boring machining on higher material removal, so that in a development the output fine boring machining is dimensioned for a material removal of more than 0.3 mm.

Because of the high service life of the honing tool it is possible, that after finishing the output fine boring machining, the bore hole has an undersize in the range of 100 to 400 μm, preferably in the range of 0.2 mm+/−0.05 mm, and this undersize is removed preferably through the intake honing machining.

The use of the measuring device makes it possible to monitor and control the process of wear of the fine boring tool. For reaching a sufficient measuring accuracy, an appropriate compensation arrangement for the cutting edge of the fine boring tool or the boring tool is provided. Furthermore, the suggestion comprises also the chance of distributing the degree of the metal-cutting work at the fine boring tool machining between the output fine boring machining and the intake honing machining dynamically, i. e. depending on the wear. This is carried out under the condition, that the service life of the fine boring tool and the honing tool are adapted or matched to each other in order to achieve that necessary tool changes, that lead to a temporary failure of the entire machining plant, can be carried out simultaneously, and thus the tools are used perfectly. This also comprises the suggestion of adapting the service life of the fine boring tool and the honing tool to one another in such a way that, for example, the down time of the honing tool is an integral multiple of the down time of the fine boring tool, and thus the change of the honing tool is carried out simultaneously with the change of the fine boring tool. This leads to another perfection and increase of efficiency of the method.

For an economic fine machining within short cycle times, in some modifications of the method during the intake honing machining at least at times by means of geometrically undefined cutting edges material is removed with a time metal cutting volume of Q_(w)=V/t, which is clearly larger than with conventionally honing. It is particularly proposed that during the intake honing machining at least at times material is removed by metal-cutting with a specific metal-cutting volume per time of more than 20 mm³/s. V is here the work piece volume removed by metal-cutting, and t the required machining time, so that the dimension is [mm³/s]. For the volume V the approximation V≈(π(D²−d²)L)/4 applies, where d is the (smaller) diameter of the bore hole prior to the material removal, D the (larger) diameter after the material removal, and L the length of the machined bore hole or the bore hole section with enlarged diameter.

In order to be able to compare values, the time metal cutting volume is referred in this application to a standard machining time t=20 s (honing time) and a standard length L=20 mm. The time metal-cutting volume thus normalized is referred to in this application as “specific” time metal-cutting volume and is abbreviated as Q_(w) ^(s).

Considering typical cylinder bore holes with nominal diameters in the range of 70 mm to 80 mm or more, the specific time metal-cutting volume is preferably more than 22 mm³/s (for 70 mm). These typical lower limits are, as a rule, exceeded clearly. With a nominal diameter 70 mm, for example Q_(W) ^(s)>50 mm³/s, sometimes also Q_(W) ^(s)>100 mm³/s or even Q_(W) ^(s)>150 mm³/s can apply.

The following table 1 gives clues about preferably reached minimum specific time metal-cutting volumes of the intake honing machining as function of the material removal as function of the bore hole diameter.

Specific Time Metal-Cutting Volume Qw [mm³/s]

TABLE 1 Nominal diameter [mm] Material removal 60 70 80 90 Qw 0.1 9 11 13 14 Qw 0.2 19 22 25 28 Qw 0.3 28 33 38 42 Qw 0.4 38 44 50 57

High time metal-cutting volumes can be supported, among others, by unconventional high cutting speed, which again depend on the rotational speed (number of revolutions) and/or stroke speed of the honing tool.

In some modifications of the method the honing tool rotates during the intake honing machining at least at times with a rotational speed of more than 400 rpm, the number of revolutions being preferably at least at times over 800 rpm, in particular over 1200 rpm. Often the rotational speed is in the range of 1200 rpm to 2000 rpm, in exceptions even more than that.

Alternatively or additionally the honing tool, can be moved during the intake honing machining at least at times with a maximum stroke speed of more than 20 m/min, the maximum stroke speed being preferably at least at times between 30 m/min and 40 m/min, sometimes even up to 50 m/min. Therein the honing tool preferably can be widened.

The spindle drive of the honing machine is then appropriately dimensioned with regard to maximum rotational speed, maximum stroke speed and drive performance.

In some modifications of the method the honing tool is driven during the intake honing machining at least within a machining period such that a cutting speed of the cutting body relatively to the internal surface of the bore hole is more than 100 m/min. In some cases then the cutting speed during the machining period can be more than 150 m/min. As a rule, the cutting speed is, at least at times, between 200 m/min and 300 m/min or between 300 m/min and 400 m/min, respectively, in exceptions even up to 500 m/min can be useful. Cutting speeds of these dimensions (about 500 m/min) can be reached, for example, when a bore hole of 80 mm diameter is machined with a rotational speed of about 2000 rpm.

In connection with cutting means of a suitable graining thus a high material removal performance is possible, in order to keep the cycle times of the first honing machining low.

In the intake honing machining preferably rather rough-grained cutting means are used, in particular cutting means with very hard cutting grains, such as for example diamond cutting grains. During the intake honing machining preferably average grain sizes in the range between about 70 μm and about 200 μm (with diamond rails of, e.g. D76 to D181) are used to reach a high material removal performance and at the same time long service life during the intake honing machining.

In some embodiments the intake honing machining for a bore hole with a diameter D is carried out within a honing time H, for which the condition H<25 s*D/75 applies. Thus, for example, the honing time for bore holes with a diameter of up to 80 mm can be 27 seconds (s) or less. Generally, the machining takes a little longer when the diameters are larger, where also the bore holes, as a rule, are longer, than when the bore hole diameters are smaller. With bore hole diameters between 70 mm and 100 mm typical honing times of less than 30 seconds can be reached.

For performing the method, on the side of the honing devices, if necessary, suitable conventional honing machining plants can be employed. Often, a double joint rod can be used, so that the honing tool can follow the bore hole. The drive rod is coupled here via an upper joint to the honing spindle, and the honing tool is coupled via a lower joint to the drive rod.

However, it can be advantageous, to modify the suspension or coupling with regard to the high rotational speed of the intake honing spindle during the intake honing machining, occurring in preferred modifications of the method, in order to guarantee a perfect quiet rotation of the tool. For this purpose, instead of the usual honing spindles, that are equipped often with two joints (upper joint spaced from the tool and lower joint near the tool) for compensating the axial misalignment between honing spindle and bore hole, another construction of the honing spindle may be convenient. For example, instead of the usual joints, a rigid rod with rigidly coupled honing tool, a direct, rigid coupling of the honing tool to the honing spindle, a floating head, a bending rod, a bending rod with a lower joint only, or a bending rod with an upper joint only can be used.

When a rigid rod with rigidly coupled honing tool is used, or a coupling of the honing tool, also possibly rigid, directly to the honing spindle, compared with a flexible coupling of the honing tool even with a high rotational speed, a quiet rotation can be reached, so that the machining quality can be guaranteed even with large material removal. As in the method, as a rule, the position and angularity is adjusted by the coarse machining with geometrically defined cutting edges, preferably the honing tool is introduced in the bore hole to be machined centrally with reference to the target position of the bore hole axis, to avoid changes of the bore hole position and/or the angular position.

Optionally a correction of the position by means of the rigid arrangement can be provided.

The term “bending rod” is supposed to refer here to a connecting element for transmitting the rotational movement from a honing spindle to a honing tool, that is dimensioned for making small deviations from the axial parallelism between honing spindle and honing tool possible, without impairing the results of the honing operation by resulting forces. The bending rod, for example, may comprise a tube section having a multitude of regularly or irregularly arranged openings, that extend over a part of the length of the tube and a part of the circumference of the tube. These broken-through tubes are very rigid while the mass is low, and allow the desired axial misalignment. Also a thin-walled tube and/or a tube of a material with lower bending strength compared with steel materials can be used. Attaching a joint to the bending rod, if possible near the honing tool, for example between the bending rod and the honing tool (lower joint) may be convenient as by this the bending moments occurring to the tool during axial misalignment can be reduced.

The method according to the invention allows a widening of the shape tolerances and surface tolerances for fine boring. The result is here a considerably potential for saving on the side of fine boring. It is, in particular, possible, that prior to the output fine boring machining for the machining of the bore hole exactly one further bore hole machining only, in particular a coarse bore hole machining with a coarse boring tool, is provided. Typically, the coarse boring machining is dimensioned for a material removal of at least 2 to 3 mm, at most 6 to 8 mm.

With regard to the widenings of the shape tolerances and surface tolerances it may be, that, after finishing the output fine boring machining, the bore hole has a roundness in the region up to 0.08 mm, preferably up to 0.05 mm, in particular in the region of 0.03 to 0.05 mm.

With reference to the straightness of the bore hole it may be, that the output fine boring machining is executed such, that, after finishing the output fine boring machining, the bore hole has a straightness in the region of up to 0.08 mm, preferably up to 0.05 mm, in particular in the region of 0.03 to 0.05 mm.

In the same measuring interval (of up to 0.08 mm, preferably up to 0.05 mm, in particular in the range of 0.03 to 0.05 mm) preferably also the parallelism of the bore hole is located occurring after finishing the output fine boring machining.

It is also an advantage that the requirements for the average roughness of the internal surface of the bore hole can be lowered. Thus it is sufficient, that the output fine boring machining is carried out in such a way, that after finishing the output fine boring machining the internal surface of the bore hole has an average roughness in the range of 20 μm to 100 μm, in particular of 25 μm to 80 μm, preferably of 30 μm to 50 μm.

For the configuration of the fine boring tool employed in the output fine boring machining there are several alternatively used modifications, in particular the following: In a first suggestion, the fine boring tool employed in the output fine boring machining has one or more adjustable cutting edges, and one or more fixed cutting edges that are arranged with reference to each other axially staggered such, that the fixed cutting edges run ahead during a forward stroke extending into the bore hole.

In another modification exclusively several adjustable cutting edges staggered to each other in the direction of the circumference and no fixed cutting edges are provided, preferably 5 adjustable cutting edges altogether being arranged. For the positioning function or adjustment function of the cutting edges an appropriate adjustment drive is provided, for example via a connecting rod or the like.

By using a dual cutting process during the output fine boring machining, in one machining step the fixed as well as the adjustable cutting edges are used. It is provided here, that by using a fine boring tool with at least one adjustable and at least one fixed cutting edge during a forward stroke extending into the bore hole the adjustable cutting edge is retracted, and only the fixed cutting edge is in engagement with the bore hole, and during a backward stroke extending out of the bore hole the adjustable cutting edge is extended such that only the adjustable cutting edge is in engagement with the bore hole. As the forward stroke as well as the backward stroke performs metal-cutting work during the output fine boring machining, the result is an efficient method and a more efficient machining, respectively.

In this connection it is pointed out, that all characteristics and features, but also methods, described with regard to the machining plant can be transferred accordingly also with respect to the formulation of the method, and can be used according to the suggestion, and are seen as also disclosed. The same goes also vice versa, i. e., constructive, that is, device characteristics only mentioned with reference to the method can also, in the frame of the claims, be taken into consideration and be claimed for the machining plant, and count also as part of the disclosure.

These and further characteristics follow, besides from the claims, also from the description and the drawing, wherein the single characteristics each can be realized on their own or with several others in the form of sub-combinations in an embodiment of the invention and in other fields, and can be advantageous and patentable embodiments. Examples of the invention are shown in the drawing, and are explained in detail in the following.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 shows a schematic view of an embodiment of a machining plant for the combined fine boring and honing machining of cylindrical internal surfaces of bore holes in work pieces and

FIG. 2 shows an axial section through an essentially cylindrical bore hole having, after finishing the fine boring operation, a cylindrical error with diameter widenings at the end, and is measured in three axially spaced measuring levels.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a schematic view of an embodiment of a machining plant 100 for the fine machining of cylindrical internal surfaces of bore holes in work pieces by fine boring and subsequent honing. The machining plant comprises a fine boring device 120 as well as a honing device 140, that are in the example set up in a common machine bed (not shown); however, in other embodiments they may have also machine beds that are set up separately.

The fine boring device 120 comprises a fine boring spindle 122, the rigidly guided spindle axis of which is orientated essentially vertically, and that is moved vertically by means of a spindle drive 124 and can be rotated around the spindle axis. At the free bottom end of the fine boring spindle a fine boring tool 128 is coupled rigidly, to the circumference of which a cutting die of hard metal is attached serving as tip of the drill 129. By means of an adjusting device 300 the radial position (indicated by the double arrow 302) of the tip of the drill 129 can be adjusted, and thus the diameter of the bore hole to be fine-bored can be defined. The adjustment device 300 comprises here an adjustment drive 301 that is in connection with the fine boring control unit 126 via a control line 303. The axial movement and the rotational movement of the fine boring spindle as well as the adjustment (double arrow 302) of the tip of the drill are controlled via a fine boring control unit 126. In typical fine boring operations a rotational speed between about 1000 and about 3000 rpm and a feed speed between about 200 and about 1000 m/min occur. A typical cutting depth (material removal) with reference to the diameter is usually between 0.1 and 1 mm. Deviations from these typical parameter ranges are possible in exceptions. The fine boring device 120 shown in FIG. 1 is an output fine boring machining arranged immediately upstream of the transfer, and dimensioned for a semi finishing machining.

The two-spindle honing device 140 comprises two essentially identically constructed honing units 141A and 141B. The honing unit 141A, first in the flow of material, corresponds with the intake honing machining. Each one of the honing units has a vertical honing spindle 142A and 142B, respectively, driven through a spindle drive 144A and 144B, respectively, so that the honing spindle executes during the honing machining vertically oscillating working motions, that are superimposed by a rotational movement around the vertical rotational axis. A first honing control unit 146A and a second honing control unit 146B, respectively, control the working motions of the honing spindles. At the free bottom end of the first honing spindle 142A a first honing tool 148A is coupled with limited mobility, by means of which immediately following the fine boring operation a coarse honing operation at the fine bored bore hole can be performed. The second honing tool 148B is dimensioned for a finishing honing operation through which the desired macro shape and surface structure of the fine bored bore hole is achieved. As the construction of these honing units is basically known, it is not discussed here in detail.

The honing device 140 has several control and measuring systems for controlling or measuring the machined work piece before, during and after the honing machining. Between the fine boring device 120 and the first honing unit 141A a bore hole control device 150 is arranged that is dimensioned for defining whether the work piece coming from the fine boring device has actually been brought by the fine boring device in the intended macro shape that allows a subsequent honing machining through the honing units 141A and 141B. By means of the bore hole control unit 150 in particular a “bored control” can be carried out for defining, for example, whether the tip of the drill 129 of the fine boring device is still mostly in sound condition or is worn or broken beyond the limits of tolerance. In the case of a broken tip of the drill the defined diameter of the bore hole coming from the fine boring device would be clearly smaller than the bore hole diameter after a correct fine boring operation, so that the subsequent honing operations become more difficult, or in the worst case, impossible. Additionally, with small bore holes at the beginning of the honing machining, collisions of the first honing tool 148A with the work piece may occur that should be avoided. As for the “bored control” only a qualitative or rough quantitative control with an accuracy in the range of about 50 μm is sufficient or exceeds this, the bore hole control device can be constructed rather simply. Suitable bore hole control devices exist at many conventional honing plants, and can be used for this purpose.

Furthermore, the honing device has a measuring device 160 integrated in the first honing unit 141A, the measuring device serving for the intake control of the fine bored bore hole coming from the fine boring device as well as also for monitoring the machining progress in the course of the first honing operation. The measuring device 160 is configured as pneumatically working “aerial measurement system”. It comprises a pair of measuring nozzles 161 arranged at the honing tool 148A diametrically opposite between the honing sticks 149. An air flow is guided to the measuring nozzles, for example via a ring distributor. The air pressure prevailing in the system is analyzed within the measuring device and makes it possible to measure the distance between the air measuring nozzles 161 and the bore hole wall. The measuring range of typically suited air measuring systems reaches, as a rule, up to about 150 μm (in special cases up to about 300 μm), wherein with the dynamic system a measuring accuracy in the dimension between about 2 μm and 5 μm can be reached.

The measuring device 160 is connected to the control unit 180 via the measuring line 304, and transmits via this measuring line 304 bore hole measuring signals representing the properties of the fine bored bore hole, for example appropriate dimension information such as diameter of the bore hole, roundness of the bore hole, straightness of the bore hole, parallelism of the bore hole or the coarseness of the internal surface of the bore hole.

Instead of integrating the measuring device 160 in the first honing unit 140A, configured for the intake honing machining, in an alternative concept (not shown) it is provided that a separate, that is independent measuring station associated with the honing devices is realized, that also determines the pre-described bore hole measuring values and transmits them via a measuring line to the control 180.

The control 180 performs a variance comparison based on the transmitted bore hole measuring signals or measuring values, and then edits a corresponding correction position to the fine machining control unit 126.

The fine boring tool has a cutting edge 129 movable by an adjusting drive 301. The adjusting drive 301 is connected via a control line 303 either directly with the control 180 or with the fine boring control unit 126. Via the control line 303 the correction position gets to the adjusting drive 301, based on which then a radial positioning of the tip of the drill 129 is performed. Thus it is possible to compensate wear at the tip of the drill 129 automatically or also to distribute the metal cutting work dynamically between boring and honing tool.

Both solutions, i. e. the solution where a measuring device 160 is integrated in the honing tool as well as also the arrangement of a measuring device in a separate measuring station of the honing device, wherein the received bore hole measuring signal serves for compensating or correcting of the position of the tip of the drill 129 and cutting edge 29, respectively, by the adjusting drive 301, can be convenient depending on the case of application.

In particular an automatic tracing of the position of the tip of the drill 129 is provided in a development.

The second honing unit can also have a measuring device appropriately constructed or working according to another measuring principle with measuring sensors integrated in the honing tool 148B, however, for the present invention also a configuration without integrated measuring device is possible.

In the direction of material flow after the honing units a verifying device 170 is arranged, a verifying head 171 being part of it that can be introduced in the finished honed bore hole, sometimes moved within the bore hole and again drawn out of the bore hole by means of a measuring spindle 172. The verifying device 170 is connected signal transmitting with the superior control 180 of the honing device, so that the information about diameter, macro shape and surface quality of the bore hole contained in the verifying signal of the verifying device is processed via the honing control 180, and can be used for controlling the honing machining by means of the honing spindles.

The fine boring control unit 126 is connected signal transmitting with the control 180 of the honing device. Thus it is in particular possible to process the signals originating in the measuring device 160 of the honing device for controlling the operation of the fine boring device. The functions of the fine boring control unit 126 and the control 180 of the honing device can be integrated within the entire control device of the machining plant, for example in a control computer. When an appropriate interface is inserted, also a separate configuration is possible, so that, if necessary, an essentially independently constructed fine boring device with an essentially independently constructed honing device can be used for constructing a machining plant according to the invention, if there is the possibility of returning the bore hole measuring signal of the honing device to the fine boring device.

The machining plant 100 can work as described in the following. The operation of the machining plant is described in an example by means of the machining of a motor block 130 for a combustion engine containing several cylinder borings 131 the internal surfaces 132 of which are supposed to be machined by fine boring and subsequent honing to serve, after finishing the honing machining, as sliding partner for the piston rings of the engine. The work piece 130 is clamped on a not-shown clamping slab, and is moved by means of suitable conveying devices in the direction of material flow 135 to the single machining stations of the machining plant and away from them.

First, the work piece 130 is brought in a position for the fine boring machining that allows to introduce the fine boring tool 128 by a vertical downward movement of the fine boring spindle in the bore hole 131. Then the bore hole 131 is fine bored by means of the fine boring tool 128 to produce a fine bored bore hole that has, compared with the desired target shape after the end of the honing machining, a rather large undersize of, for example, 200 μm in the diameter. In order to reach the desired diameter, the radial position of the tip of the drill is adjusted by means of the fine boring control 126 until the desired end value. When the fine boring operation has been finished, the tip of the drill is retracted, and the fine boring tool is pulled upward out of the fine bored bore hole.

After that, the work piece 130 is shifted in the area of the bore hole control device 150. This checks by means of a control sensor whether the diameter of the fine bored bore hole is above a given limit, so that an introduction of the honing tools in the subsequent honing steps is possible without risk. If the tip of the drill has been broken during the fine boring operation, or the fine boring tool is not able anymore, because of wear, to produce a sufficient internal diameter, the insufficiently bored work piece is taken out of the material flow. In the example, a disc is used as control device having an external diameter that just can be introduced in the smallest bore hole diameter that is just possible for securing the honing process. A binary sensor determines by means of the final position control, whether the control device has been introduced completely in the bore hole. If the bore hole is too narrow, the disc cannot be introduced, so that the final position sensor does not give a release signal (go signal).

Work pieces with sufficient internal dimension of the fine bored bore hole are shifted in the dashed drawn machining position below the first honing unit 141A such that the honing tool 148A can be introduced in the fine bored bore hole by lowering the honing spindle.

After that, the first honing tool 148A is introduced in the fine bored bore hole by lowering the first honing spindle 142A. By means of the measuring device 160 then a quantitative dimensional measuring of the fine bored bore hole is performed, the measuring result being transmitted in the form of bore hole measuring signals to the control unit 180 of the honing device. This is configured such that the bore hole measuring signal or a signal deduced from it can be transmitted to the fine boring control unit 126, so that the fine boring device 120 can be controlled via the fine boring control unit depending on the bore hole measuring signal. An example for a highly accurate dimensional measuring of a fine bored bore hole is explained in detail by means of FIG. 2.

In many cases, several tenths of seconds to seconds, that are required for bringing the adjustable machining elements at the honing tool from their retracted position radial to the outside in machining engagement with the internal wall of the bore hole that has to be machined, pass between the program-controlled start of the honing operation and the start of a substantial material removal by the honing. Within this period of time, the honing tool may already be partly or completely introduced in the bore hole, however, the material removal has not yet started, so that the fine bored bore hole is not yet or not essentially changed. In advantageous modifications this time is also used for capturing bore hole measuring signals, so that, for example the measuring takes place, at least at times, simultaneously with the adjustment of the machining tools at the honing tool. If necessary, the measurement can extend without interruption until the starting phase of the material-removing machining, so that, if necessary, a direct transition between the capturing of the bore hole measuring signal to the output control of the fine boring operation and an in-process measurement of the subsequent honing machining takes place.

In all cases the measuring device 160 of the honing device serves immediately after finishing the fine boring operation and before the beginning of the material-removing honing operation as output control for checking the result of the machining of the fine boring operation and, at the same time, as intake control for the subsequent honing operation. If the bore hole measuring signal has the result that the macro shape of the fine bored bore hole obtained by the fine boring is not within the given tolerance range, the operation of the fine boring device can be controlled, for example through adjusting the radial stopping position of the tip of the drill 129 such that during the subsequent machining of a next work piece the resulting macro shape of the fine bored bore hole after finishing the fine boring operation is in the desired tolerance range.

After this output control of the fine boring and intake control for the honing operation the coarse honing operation, carried out by means of the first honing unit 141 A, starts by means of which the internal surface 132 of the bore hole 131 receives an altered surface structure (with crisscrossed machining marks), compared with the fine boring, as well as a macro shape that is closer to the target shape, with slightly larger internal diameter. The machining result of the coarse honing operation can be checked during the coarse honing and/or after finishing the coarse honing by means of the measuring device 160. In particular, basing on the corresponding measuring signal, the coarse honing operation can be stopped, when the macro shape, desired after the coarse honing, or the diameter of the bore hole, desired after the coarse honing, is reached.

After that the first honing tool 148A is moved out of the bore hole, and the work piece is moved in a position associated with the second honing unit 141 B that allows introducing of the second honing tool 148B in the bore hole. After lowering the second honing tool 148B in the bore hole, the material-removing finishing honing operation is performed by which the bore hole gets the desired target shape and surface structure. The finishing honing operation can also be monitored by means of a measuring device, and, if necessary, depending on a corresponding measuring signal, be controlled.

After the end of the finishing operation and retracting the second honing spindle out of the work piece, the work piece is shifted in the direction of the verifying device 170, that is installed for measuring the finished fine bored bore hole 131 and for checking, whether the diameter, the macro shape of the bore hole 131 and/or the surface structure of the internal surface 132 complies with the specifications of the machining process. By a returning of appropriate verifying signals to the control 180 of the honing machine, an improvement of the constancy of the machining process can be reached, so that variations in the quality of machined bore holes compared with conventional machining plants can be reduced.

An example for a highly accurate dimensional measuring of a fine bored bore hole 231 in a work piece 230 is explained in more detail by means of FIG. 2. The ideally circular cylindrical internal surface 232 has received a shape differing significantly from a circular cylinder shape by the fine boring process with a waist in the axial center area of the bore hole as well as with diameter widenings to the respectively open end areas of the bore hole. After shifting the work piece in the area of the first honing unit, the honing tool 248 is lowered so far in the bore hole 231 until the diametrically opposed air measuring nozzles 261A, 261B of the measuring device have reached a measuring level Z3 near the top intake area of the bore hole 231 facing the spindle. After stopping the vertical feeding motion, the honing tool 248 is rotated in the bore hole essentially symmetrically around the bore hole axis 233 by at least 180°, in order to define the diameter of the bore hole on level Z3. By means of a revolution detector for the honing spindle it is possible, to capture the rotatory angle values of the honing tool associated with the diameter values, so that also an angle dissolving measurement of the diameter in the area of the respective measuring level is possible. Information about the bore hole shape in the measuring plane can be deduced from that. After finishing the measuring, the honing tool is lowered further, so that the measuring sensors 261A, 261B are in the axial center area of the bore hole near the measuring level Z2. After that, the corresponding, if necessary angle dissolving, diameter measuring process is repeated. A third measuring takes place after that on the level Z1 near the end of the bore hole opposite the spindle. The measuring results are evaluated for defining the macro shape of the bore hole. If the result of this evaluation is, that the macro shape is outside the specification given for the fine boring process, the fine boring tool is adjusted anew by shifting the tip of the drill or exchanged, in order to get in the subsequent work piece a macro shape of the fine bored bore hole within the specification.

The machining plant and the described method make it possible to execute a very stable machining process, where the machined work pieces show only very small quality variations. Possible deviations from the ideal machining process, primarily by wear of the machining tools, can be recognized very soon and be compensated on short notice by means of returning the appropriate measuring signals to the single machining units by adjusting the machining tools an/or exchange of machining tools.

The invention has been explained by means of an embodiment where the honing device executes after the fine boring at least in the first honing operation a honing machining with axially oscillating and rotatory movement of the honing tool. In other embodiments, at the honing device other devices for producing defined surface qualities are provided. For example, a laser unit can be integrated for executing a surface structuring by means of laser irradiation. Laser irradiation can also be used to change areas near the surface of the machined work piece surface by supplied energy on a large scale, for example to harden. Also a brushing device for brushing the surfaces can be integrated. In other embodiments, during the production of defined surface structures and other defined surface qualities the conventional honing can be deleted completely, for example, by using one or more of the mentioned methods for a finishing surface highly fine machining in the honing device. The terms “honing device” and “honing tool” thus stand in place for finishing machining methods or finishing machining tools that can be used after a fine boring operation for machining the fine bored bore hole metal cutting or without removing metal, and to bring it in a desired finished condition.

The honing device is configured with multiple steps, for example with two or three steps, and therefore comprises a corresponding number of honing devices arranged one after the other that can also be configured redundantly.

Although the invention has been described in terms of specific embodiments which are set forth in considerable detail, it should be understood that this is by way of illustration only and that the invention is not necessarily limited thereto, since alternative embodiments and operating techniques will become apparent to those skilled in that art in view of the disclosure. Accordingly, modifications are contemplated which can be made without departing from the spirit of the described invention. 

1. Method for the fine machining of internal surfaces of bore holes in work pieces by fine boring and subsequent honing with the following steps: Fine boring of at least one bore hole of a work piece by means of a fine boring tool of a fine boring device for manufacturing of a fine bored bore hole; Transfer of the work piece in a honing device for machining the fine bored bore hole by means of a honing tool of the honing device; Measuring the fine bored bore hole by means of a measuring device allocated to the honing device for manufacturing of at least one bore hole measuring signal representing the properties of the fine bored bore hole; and Controlling the operation of the fine boring device depending on the bore hole measuring signal, wherein an output fine boring machining arranged immediately upstream of the transfer is designed as semi-finish machining and is carried out using a fine boring tool having at least one adjustable cutting edge, with the position of the adjustable cutting edge being controlled depending on the bore hole measuring signal, and wherein during an intake honing machining arranged downstream of the transfer an oversize of at least 100 μm is removed.
 2. The method of claim 1, with an intake honing machining being provided and wherein with reference to the diameter of the bore hole, during said intake honing machining, with reference to the diameter of the bore hole, an oversize of a maximum of 400 μm is removed, the maximum oversize removed by said intake honing machining preferably being less than 300 μm.
 3. The method of claim 1, with the work piece having a machining position in the honing device, wherein measuring the fine bored bore hole by means of the measuring device is carried out in the machining position of the work piece in the honing device.
 4. The method of claim 1, wherein the output fine boring machining is dimensioned as semi finish machining defining position and angle.
 5. The method of claim 1, wherein the output fine boring machining is designed for a material removal of more than 0.3 mm.
 6. The method of claim 1, with after finishing the output fine boring machining the bore hole having an undersize, wherein the undersize is in the range of 100-400 μm, preferably in the range of 0.2 mm+/−0.05 mm.
 7. The method of claim 1, with a dynamic allocation of the metal-cutting machining between the output fine boring machining and the honing device, and the intake honing machining, respectively, being provided and wherein the dynamic allocation of the metal-cutting machining between the output fine boring machining and the honing device, and the intake honing machining, respectively, is provided under the condition that the service life of the fine boring tool and the honing tool can be adjusted or adapted to each other.
 8. The method of claim 1, with during the intake honing machining at least at times material being removed by metal-cutting with a specific metal-cutting volume per time and wherein at least at times material is removed by metal-cutting with the specific metal-cutting volume per time of more than 20 mm^(3/s.)
 9. The method of claim 1, with a bore hole with a diameter D being provided and the intake honing machining for the bore hole with the diameter D being carried out within a honing time H, wherein the intake honing machining for the bore hole with the diameter D is carried out within the honing time H with the condition H<25 s*D/75.
 10. The method of claim 1, with for coupling the honing tool used for intake honing machining to the honing spindle a double joint rod with a drive rod being coupled to the honing spindle via an upper joint and with the honing tool being coupled to the control rod via a lower joint being used, wherein for coupling the honing tool used for intake honing machining to the honing spindle the double joint rod with the drive rod is coupled to the honing spindle via the upper joint, and the honing tool is coupled to the control rod via the lower joint.
 11. The method of claim 1, wherein prior to the output fine boring machining for the machining of the bore hole one single further boring machining, in particular a coarse boring machining with a coarse boring tool is provided.
 12. The method of claim 1, with prior to the output fine boring machining for the machining of the bore hole one single further boring machining, in particular a coarse boring machining with a coarse boring tool being provided and wherein said coarse boring machining is designed for material removal of at least 2 to 3 mm, at most 6 to 8 mm.
 13. The method of claim 1, wherein the output fine boring machining is carried out such that after finishing the output fine boring machining the roundness of the bore hole is in the range of up to 0.08 mm, preferably of up to 0.05 mm, in particular in the range of 0.03 to 0.05 mm.
 14. The method of claim 1, wherein the output fine boring machining is carried out such, that after finishing the output fine boring machining the straightness of the bore hole is in the range of up to 0.08 mm, preferably of up to 0.05 mm, in particular in the range of 0.03 to 0.05 mm.
 15. The method of claim 1, wherein the output fine boring machining is carried out such, that after finishing the output fine boring machining the parallelism of the bore hole is in the range of up to 0.08 mm, preferably of up to 0.05 mm, in particular in the range of 0.03 to 0.05 mm.
 16. The method of claim 1, wherein the output fine boring machining is carried out such, that after finishing the output fine boring machining the internal surface of the bore hole has an average coarseness in the range of 20 μm≦R_(z)≦100 μm, in particular of 25 μm≦R_(z)≦80 μm, preferably of 30 μm≦R_(z)≦50 μm.
 17. The method of claim 1, wherein the fine boring tool used during the output fine boring machining has one or more adjustable cutting edges and one or more fixed cutting edges, that are arranged staggered axially with reference to each other, such that the fixed cutting edges run ahead during forward stroke extending into the bore hole.
 18. The method of claim 1, with a fine boring tool being used during the output fine boring machining and wherein said fine boring tool has several adjustable cutting edges staggered to each other in the direction of the circumference, but no fixed cutting edge, preferably with five adjustable cutting edges being provided.
 19. The method of claim 1, wherein during the output fine boring machining a dual cutting method using a fine boring tool with at least one adjustable and at least one fixed cutting edge is carried out, and wherein during a forward stroke extending into the bore hole the adjustable cutting edge is retracted and only the fixed cutting edge is in engagement with the bore hole, and during a backward stroke extending out of the bore hole the adjustable cutting edge is extended such that the adjustable cutting edge only is in engagement with the bore hole.
 20. Machining plant for fine machining cylindrical internal surfaces of bore holes in work pieces by fine boring and subsequent honing with a fine boring device comprising at least one fine boring spindle equipped for carrying a fine boring tool, and a fine boring control for controlling the operation of the fine boring device, and a honing device with at least one honing spindle equipped for carrying a honing tool, as well as a honing control for controlling the operation of the honing device, wherein the honing device has at least one measuring device for measuring a fine bored bore hole machined by the fine boring device, and for generating a bore hole measuring signal representing the properties of the fine bored bore hole, and wherein the fine boring control is configured for controlling the operation of the fine boring device depending on the bore hole measuring signal, characterized in that the machining plant is set up for executing the method according to any of the preceding claims. 